Matthew Henry on Isaiah 26:1-4

"That day," seems to mean when the New Testament Babylon shall be levelled with the ground. The unchangeable promise and covenant of the Lord are the walls of the church of God. The gates of this city shall be open. Let sinners then be encouraged to join to the Lord. Thou wilt keep him in peace; in perfect peace, inward peace, outward peace, peace with God, peace of conscience, peace at all times, in all events. Trust in the Lord for that peace, that portion, which will be for ever. Whatever we trust to the world for, it will last only for a moment; but those who trust in God shall not only find in him, but shall receive from him, strength that will carry them to that blessedness which is for ever. Let us then acknowledge him in all our ways, and rely on him in all trials.